Question 376250
8+11+6+6=31 marbles total.
nCr=Combination of n things taken r at a time=n!/((n-r)!r!)
. 
(11C4*20C1 + 11C5)/31C5
=((330*20)+462)/169911
=(6600+462)/169911
=7062/169911
=0.0416
.
Ed